1. Field of the Invention
The present invention relates to a process for preparing cephalosporin derivatives, including cefprozil and its salt, using a 3-(Z)-propenyl cephem derivative stereospecifically prepared.
2. Description of the Related Art
3-(Z)-propenyl cephem derivative is a compound useful as an intermediate for preparation of cefprozil which is an oral cephalosporin antibiotic. Various preparation processes thereof have been known.
WO93/16084 discloses a process for selectively separating a 3-(Z)-propenyl cephem compound by means of a hydrochloride, metal, or tertiary amine salt of 7-amino-3-(1-propen-1-yl)-3-cephem-carboxylic acid or by adsorption chromatography. However, there is a disadvantage in that separation and purification are cost-ineffective.
U.K. Patent No. 2,135,305 discloses a process for preparing cefprozil from a 4-hydroxyphenylglycine compound with a t-butoxycarbonyl-protected amino group and a cephem compound with a benzhydryl-protected carboxyl group. However, incorporation of a 3-propenyl group after acylation lowers reaction efficiency and high-performance liquid chromatography is required for isomer separation, which render industrial application difficult.
U.S. Pat. No. 4,727,070 discloses a technique of removing an E-isomer cefprozil from a mixture of Z/E cefprozil, which includes incorporating an active group such as sodium imidazolidinone into the mixture of Z/E cefprozil by reaction of the mixture of Z/E cefprozil with acetone, followed by deprotection. However, purification by chromatography incurs enormous costs.
In view of the above problems, Korean Patent Laid-Open Publication No. 2002-80838 discloses a process for preparing a 3-(Z)-propenyl cephem compound by reacting a phosphoranylidene cephem compound with acetaldehyde in a mixed solvent essentially consisting of ether in the presence of a base. According to a disclosure in this patent document, ether is essentially used. In this respect, in the case of using methylenechloride, tetrahydrofuran, etc., even when other reaction conditions, for example, reaction temperature, reaction duration, base, catalyst, and the like are adjusted, it is very difficult to adjust the content of the Z-isomer to more than 83%.
Korean Patent Laid-Open Publication No. 2002-69437 discloses a 4-hydroxyphenylglycine anhydride with a pivaloyl group, which is a compound useful as an intermediate for the 7-position of cefprozil, and a preparation process thereof.